Summary of studies using biosensors for mercaptopurine detection.

Cancer	Biosensor	Method	Sensitivity, quality and quantity	Advantage
ALL168	6-Thiouric acid	Electrochemical surface-enhanced Raman spectroscopy (EC-SERS)	Excellent signal for 6-TUA down to μM concentrations in synthetic urine	Detected rapidly at clinically relevant concentrations, without the need for sample pre-treatment (less than 1 minute)
ALL204	Chip-based capillary electrophoresis (CE) (CE-EC detection)	PMMA-based microfluidic chip	The detection limit of 100 nM	High detection speed, negligible sample consumption, low power requirement, easy integration
ALL171	Gold nanoparticles (AuNPs)	SPR	More sensitive for detecting different purines at a concentration of 10−7 M for 6-thioguanine and 6-mercaptopurine	High detection speed, negligible sample consumption, low power requirement, and easy integration